Add py38 job templates and make py3 templates consistent

OpenStack now uses python templates per release, like
openstack-python3-victoria-jobs.

Some projects need more fine granular control over which jobs to test,
so use:
- openstack-python38-jobs which just adds py38; this follows the pattern
  with earlier versions
- openstack-python38-jobs-no-constraints: Same jobs but without
  constraints
- openstack-python36-jobs-no-constraints: Same jobs for py36
- openstack-pep-publish-jobs to run pep8 and publishing of tarballs

Update templates openstack-python35-jobs-no-constraints and
openstack-python37-jobs-no-constraints to follow the scheme above.

If this gets approved, I'll review users of
openstack-python35-jobs-no-constraints and
openstack-python37-jobs-no-constraints and add
openstack-pep-publish-jobs-no-constraints to their Zuul configuration
wherever needed.

See also https://etherpad.opendev.org/p/-CBx0IaMT37oFBHdt8iV

Change-Id: If5ce06f620f5cd2161b752e1cc402a4e39d36e90

zuul.d/project-templates.yaml

@@ -1053,6 +1053,34 @@
         - openstack-tox-py38:
             voting: false
 
+- project-template:
+    name: openstack-python38-jobs-no-constraints
+    description: |
+      Runs unit tests for an OpenStack Python project under cPython
+      version 3.8.
+      This uses a variant that do not use constraints.
+    check:
+      jobs:
+        - tox-py38
+    gate:
+      jobs:
+        - tox-py38
+
+
+- project-template:
+    name: openstack-pep-publish-jobs
+    description: |
+      Runs the pep8 job and publishing of python tarball after merge.
+    check:
+      jobs:
+        - openstack-tox-pep8
+    gate:
+      jobs:
+        - openstack-tox-pep8
+    post:
+      jobs:
+        - publish-openstack-python-branch-tarball
+
 - project-template:
     name: openstack-python-jobs-no-constraints
     description: |
@@ -1073,8 +1101,9 @@
 - project-template:
     name: openstack-python35-jobs-no-constraints
     description: |
-      Runs the OpenStack PTI jobs for python3.5, but uses the versions of them
-      that do not use constraints.
+      Runs unit tests for an OpenStack Python project under cPython
+      version 3.5.
+      This uses a variant that do not use constraints.
     check:
       jobs:
         - tox-py35:
@@ -1083,26 +1112,32 @@
       jobs:
         - tox-py35:
             nodeset: ubuntu-xenial
-    post:
+
+- project-template:
+    name: openstack-python36-jobs-no-constraints
+    description: |
+      Runs unit tests for an OpenStack Python project under cPython
+      version 3.6.
+      This uses a variant that do not use constraints.
+    check:
       jobs:
-        - publish-openstack-python-branch-tarball
+        - tox-py36
+    gate:
+      jobs:
+        - tox-py36
 
 - project-template:
     name: openstack-python37-jobs-no-constraints
     description: |
-      Runs the OpenStack PTI jobs for python3.7, but uses the versions of them
-      that do not use constraints.
+      Runs unit tests for an OpenStack Python project under cPython
+      version 3.7.
+      This uses a variant that do not use constraints.
     check:
       jobs:
-        - tox-pep8
         - tox-py37
     gate:
       jobs:
-        - tox-pep8
         - tox-py37
-    post:
-      jobs:
-        - publish-openstack-python-branch-tarball
 
 - project-template:
     name: openstack-lower-constraints-jobs